It is known that a silver halide photographic light-sensitive material is subjected to heat development to form an image as described, for example, in Shashin Kogaku no Kiso &lt;Higin-en Shashin&gt; (The Fundamentals of Photographic Engineering &lt;Non-silver Salt Photography&gt;), pages 242 to 255, Corona Publishing Co., Ltd. (1982) and U.S. Pat. No. 4,500,626.
It is also known that a heat developable light-sensitive material using silver halide has excellent photographic properties such as sensitivity and gradation in comparison with electrophotography or diazo photography. Various methods for obtaining a color image using a silver halide light-sensitive material have been proposed. Among them, a color development processing method wherein a dye image is formed upon a coupling reaction of an oxidation product of a color developing agent with a coupler is known. With respect to the color developing agent and coupler used in the color development processing method, a combination of a p-phenylenediamine reducing agent with a phenolic or active methylene coupler as described in U.S. Pat. No. 3,531,256, a p-aminophenol reducing agent as described in U.S. Pat. No. 3,761,270, and a combination of a sulfonamidophenol reducing agent with a four-equivalent coupler as described in U.S. Pat. No. 4,021,240 are proposed.
However, the color development processing method has problems in that printout of undeveloped silver halide remaining after processing and coloration of the undeveloped area for a lapse of time occur and in that color turbidity due to the presence of both reduced silver and color image in the exposed area is observed. In order to solve these problems, a dye transfer method wherein a diffusible dye is formed by heat development and the dye is transferred into an image receiving layer is proposed.
Of such diffusion transfer heat developable light-sensitive materials, there are a case wherein the light-sensitive material comprises an image receiving layer which is acceptable a dye on the support thereof and a case wherein the image receiving layer is provided on a support different from the support of the light-sensitive material.
In case of using heat developable color light-sensitive materials, it is particularly preferred to conduct the diffusion transfer of diffusible dye into a dye receiving layer provided on a support of an image receiving material simultaneously with or after the formation of diffusible dye in order to obtain dye images having high color purity.
Further, a method has been proposed in which a diffusible dye is released or formed imagewise by heat development and the diffusible dye is transferred into a dye fixing element. According to the method, either a negative dye image or a positive dye image can be obtained by changing the kind of dye-providing compound used or the kind of silver halide used. More details thereof are described, for example, in U.S. Pat. Nos. 4,500,626, 4,483,914, 4,503,137 and 4,559,290, JP-A-58-149046 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-60-133449, JP-A-59-218443, JP-A-61-238056, EP-A-220,746, JIII Journal of Technical Disclosure No. 87-6199, and EP-A-210,660. However, the method is disadvantageous in that sensitivity of the light-sensitive element decreases since the dye-providing compound which contains a previously colored dye is employed. Therefore, it is preferred to conduct a method in which a dye is first formed by a reaction of a colorless coupler with a color developing agent and the dye formed is diffused.
The methods of forming an image by the coupling process as described above are also proposed. For instance, heat developable light-sensitive materials containing a color developing agent precursor which releases a p-phenylenediamine and a coupler as described, for example, in JP-B-63-36487 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-5-224381 and JP-A-6-83005, a combination of a ureidoaniline reducing agent with an active methylene coupler as described in JP-A-59-111148, and a light-sensitive material using a coupler which has a coupling-off group containing a polymer chain and releases a diffusible dye upon color development as described in JP-A-58-149047 are proposed.
However, when the color developing agents or color developing agent precursors as described in the above described patents are employed, a problem in that the dyes formed have poor light-fastness during storage occurs in addition to the insufficient color image density after transfer. Accordingly, development of a technique which meets both the image fastness and color image density after transfer has been desired.